The goal of the Treatment Services Core is to promote and support HIV-related health and mental health services research that will enhance our understanding of the complex health delivery systems used by persons at risk for or infected with HIV. In addition, it will support innovative research to make these systems more effective at providing accessible, high quality, and cost- efficient prevention and care. Disparities exist in the access and quality of HIV care provided to African-American and Latino individuals with low income compared to persons of other ethnic groups. The disparities in HIV services reflect long-term inequities to the access and utilization of health and mental health care, which has lead to significant community mistrust, particularly towards researchers. Therefore, it is essential to CHIPTS that all research be conducted within collaborative, long-term relationships with representatives of the affected communities. This is operationalized by the Center through a Participatory Action Research (PAR) model, These disparities arise from many sources, but often our research has focused on deficits in the individual's HIV-related knowledge, attitudes, or beliefs rather than focusing on structur4al factors or the organization of care (e.g., providers' attitudes and behaviors, funding streams, density of available services in a geographic region). Far more research needs to be focused on the system-of-care for HIV and the settings and providers delivering both prevention and treatment services. This is particularly important in order to assess the access, utilization, and quality of HIV care for persons with comorbid disorders and for immigrants. For consumers with multiple needs, it will be necessary to develop coordinated, comprehensive, and continuous models of integrated HIV services. The Treatment Services Core aims to increase our understanding of, and interventions for, providers within health and mental health settings, particularly for subpopulations with comorbid disorders. Finally, while our understanding of current HIV systems-of-care is limited, the system is undergoing dramatic change. Since the identification of the first case of AIDS, there has been a revolution in the health care industry with about one-third of care in California being managed. Medicaid services for HIV infected adults is carved out in LA and provided in specialty HIV-settings or private settings. More recently, the Internet has begun to change and will change in the future a number of aspects of health care delivery, from routine tasks such as keeping patient records to the interaction of doctors and patients through e-mail. The delivery of HIV care in rural and international settings may potentially be improved through the utilization of electronic and web technologies. It is critical to anticipate how the web and such adaptations as telemedicine will impact the delivery of prevention and treatment services. The Treatment Services ore will begin to identify these issues and set a research agenda to be implemented over the how CHIPTS within health and mental health care delivery settings.